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I'm working with largish PDFs (e.g. 17523x2383 dots @ 72dpi), where i need to zoom out (to see the overall picture and to navigate) and to zoom in (to read labels on the nodes).

The PDFs are simple graphs (generated from gv) containing mostly text, text-boxes and lines, andthe occasional thumbnail image. The only thing special about them is there size.

I don't think, that the graphics are complicated to render, e.g. using the xdot.py program to visualize the gv graphs (before they are rendered into a PDF) is blindingly fast, so I can scroll and zoom arbitrarily in realtime.

Unfortunately, it seems that all all PDF readers (that I have tried) have problems with such formats.

Afaict, I require the the following features: - fast renderer (so it can be used interactively) - zoom in to >100% (ideally unlimited) - zoom out to <2% (ideally unlimited) - when zooming, keep focus - minimal dependences (i'm running xfce4; i'd rather not pull in half of kde or gnome just to display a PDF) - free software (FLOSS)

These are the readers that i've tried:

  • evince: renders the complete page nicely (at a zoom-level 4.93%), but refuses to zoom in to more than 41.47%)

  • vprerex: only has 6 fixed zoom-levels between 100% and 400%, thus not allowing me navigate.

  • mupdf: limits zoom-out to 25%; more importantly, I haven't found a way to keep a given point focused, when using the scroll-wheel to zoom-in, thus making it impossible to navigate the page.

  • firefox built-in PDF reader: while it limits zoom-out with the mouse-wheel to 25%, it also allows for a zoom to page-width which allows for an overall view of the image, and then to zoom in (until 1000%) ata select spot. unfortunately, rendering at any size where the font is big enough to be readable (e.g. 70% and above) makes the image very blury

  • atril limits zoom-in to 50%

  • qpdfviewer loses focus when zooming; takes ages to render a new zoom level

  • Adobe PDF reader is not free/libre/open-source

So my question is: is there a free (as in Free/Libre/OpenSource Software) PDF reader that allows for arbitrary and interactive zoom in/zoom out?

  • Any dependencies OK? Then you could take a look at Okular (KDE). I'm currently not at my machine, so I cannot check for "arbitrary zoom" – but zoom it does :) – Izzy May 31 '16 at 16:27
  • okular does indeed handle the zoom nicely, though KDE is a bummer: it doesn't exactly match the minimal dependencies requirement; apart from that it is probably the best viewer for this specific task. – umläute May 31 '16 at 19:57
  • So shall I expand it as answer, despite of "violating" the minimal dependencies? I'm curious for other answers myself: if there's anything coming close to Okular, my chances to get rid of all the KDE libs on my next install would dramatically increase :) – Izzy May 31 '16 at 21:36
  • have u tried foxit? be careful when installing it not to add any bells and whistles, just the vanilla viewer. – user24088 Jun 1 '16 at 7:12
  • @Izzy I ended up using okular for my tasks; so if you expand your comment to an answer, i will accept it. – umläute Sep 6 '17 at 8:36
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As requested, converting my comments to an answer:

If you can live with all the KDE dependencies it requires (e.g. because you're using KDE anyway),¹ you can use Okular for this. It handles zooming fine, and beside PDF also supports a bunch of other formats (e.g. EPUB). Okular is the default document viewer used by the KDE project. It meets most of your requirements:

  • fast renderer: to my experience, yes.
  • zoom in to >100% (ideally unlimited) - zoom out to <2% (ideally unlimited): didn't check the percentage's lower limit, but > 100% I can confirm
  • when zooming, keep focus: at least when scrolling with the mouse, AFAIR
  • minimal dependences: unfortunately requires a bunch of KDE libs
  • free software (FLOSS): yes.

I've meanwhile abandoned all KDE dependencies and mostly use qPDFviewer (which you already ruled out as it loses focus on zooming), so I can no longer cross-check – but my requirements differ from yours.


¹ Though your question points out the opposite, in your comments you've acknoledged it would be OK :)

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There is xpdf. Though it zooms to only 4x size, you can select a rectangular area and zoom to selection of any size. At the zoom level you can pan in any direction to view the whole page.

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PDF Studio Viewer, which is a free PDF Reader for Linux, can zoom from 10% to 6400%. It also has a loupe tool that can be used to look at fine details in the file at high zoom levels.

Disclosure: I am a developer at Qoppa Software.

  • it seems that this is only "free as in beer", as opposed to free (as in Free/Libre/OpenSource Software) (as requested), which I meant to read "free as in speech" – umläute Nov 5 '17 at 20:09

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